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Sample Size Determination

Client's mean income: What sample size for 95% and 99% level of confidence

A social service agency plans to conduct a survey to determine the mean income of its clients. The director of the agency prefers that you measure the mean income very accurately, to within + or - $500 from a sample taken 2 years ago, you estimate that the standard deviation of income for this population is about $5000 your job

Some stats problems

1. The amounts (in ounces) of juice in eight randomly selected juice bottles are: 15.4 15.7 15.2 15.8 15.8 15.4 15.0 15.6 Assuming the population of amounts in juice bottles is known to be normally distributed, create a 95% confidence interval estimate for , the mean amount of juice in all bottles. You will b

Sample Size and Population Mean

Q1: Why does the sample size play such an important role in reducing the standard error of the mean? What are the implications of increasing the sample size? Q2: Why might one be interested in determining a sample size before a study is undertaken? How do population variability and a level of certainty affect the size of

Investor Deposits: Sample Size Calculation - Confidence Interval

An investment firm with 10,000 clients would like to accurately forecast the average dollar amount their current customer will deposit over the coming year. They decide to telephone a random selection of 25 of their customers to ask how much they plan to deposit, and they would like to keep this sample as small as possible so th

Sample Size

How I would obtain a 150 representative sample size?

Sample Size for estimating population mean

In order to be accepted into a top university, applicants must score within the top 5% on the SAT exam. Given that SAT test scores are normally distributed with a mean of 1000 and a standard deviation of 200, what is the lowest possible score a student needs to qualify for acceptance into the university? A) 1330 B) 1400 C

Sample size calculation explained in this answer

1. The Arkansas State Police wish to estimate the average mph being traveled on the interstate highways, which cross the state. If the estimate is to be within 8 mpg of the true mean with 98% confidence and the estimated standard deviation is 22 mph, how large a sample size must be taken? 2. The odds in favor of an event ar

Finding Sample Size.

Sample Size for Weights of Quarters The Tyco Video Game Corporation finds that it is losing income because of slugs used in video games. The machines must be adjusted to accept coins only if they fall within set limits. In order to set these limits, the mean weight of quarters in circulation must be estimated. A sample of qu

Sample size problem set

Please see the attached file. A company wants to conduct a telephone survey of randomly selected voters to estimate the proportion of voters who favor a particular candidate in a presidential election, to within 2% error with 95% confidence. It is guessed that the proportion is 53%. 1. What is the required minimum sampl

Sample Size Determination for an Insurance Company

1) In order to set rates, an insurance company is trying to estimate the number of sick days that full time workers at an auto repair shop take each year. A previous study indicated the standard deviation was 2.8 days. How large a sample must be selected if the company wants to be 95% confident that the true mean differs from th

Calculations for Probabilities in Excel

In computing sample size for estimating population proportions, the formula involves p(1-p) (where we don't know p). We use p = ½ if we don't know anything about it, since that is a "worst case". Find the values of p(1-p) for p=.01, .02, .05, .10, .15, .20, .30, .40., .50, .60, .70,.80, .85, .90, .95, .98, and.99. Be prepared t

Three questions on statistics, sampling, and strata

Chapter 6 (Book "Sampling of Populatations" 3rd edition) 1. Ester is an epidemiologist and body builder She is planning a survey of Chicago area body builders to determine the proportion who have ever used anabolic steroids. Her sampling frame consists of membership lists obtained from all accredited health clubs in the six

Statistics : Choosing Sample Size

Select one of these articles and provide an overview of the contents and apply the concepts to the Job Satisfaction survey. It is important to cover the concept of the techniques used to estimate sample size. Simple rules shape proper sample size Section: Special report RESEARCH ? A numbers game How low can you go? No,

Sample Size of Americans Who Own Their House

The CEO of a company wants to estimate the proportion of Americans who own their house. What sample size should be obtained if he wants the estimate to be within 0.02 with 90% confidence if a. He uses an estimate of 0.675 from the American Census Bureau? b. He does not use any prior estimates?

Statistics and Business - Sample Size

Business Problem Paper and Optional Presentation a. Clearly define the dependent and independent variables that are the focus of the team's study. The dependent variable is the variable whose value is the result or is a function of the control or independent variables. b. State the null and alternative hypotheses and the


See attached file for full problem description. 16. A study of 305 computer chips found that 244 chips functioned properly. Develop a 99 percent confidence interval for the population proportion of properly functioning computer chips. 17. A correctional institution would like to report the mean amount of money spent per d

How many in the workforce should be interviewed to meet your requirements?

You plan to conduct a survey to find what proportion of the workforce has two or more jobs. You decide on the 95 percent confidence level and state that the estimated proportion must be within 2 percent of the population proportion. A pilot survey reveals that 5 of the 50 sampled hold two or more jobs. How many in the workforce

Find minimum sample size

Find the appropriate minimum sample size: You want to be 95% confident that the sample variance is within 40% of the population variance. Sample size must be an integer.


What are the elements that affect determination of sample size?

Bank Survey - sample size

Bea asks Brian the sample size and the timeframe. Brian responds, 140,000 Suppose the bank has one million customers in the USA (where the survey is conducted) With a 95% confidence level and a margin of error of 3%, what would you recommend the minimum sample size to be? This is the minimum sample size. In practi

Sample Sizes and Proportions

The Democrat and Chronicle reported that 25% of the flights arriving at the San Diego airport during the first five months of 2001 were late (Democrat and Chronicle, July 23, 2001). Assume the population proportion is p = .25 a. Show the sampling distribution of p, the proportion of late flights in a sample of 1000 flights.

Sample size estimation

A) A nutritionist wants to estimate the mean amount of cholesterol in a certain variety of chicken eggs. She wants to be within 14 mg. with 99% confidence. It is believed that the standard deviation is 25 mg. How large a sample of eggs should she use? B) A nurseryman wants to estimate how many poinsettias he will need for Ch

Determining appropriate sample sizes

Why is it important to determine an appropriate sample size and how can you determine what sample size you should use to ensure that your population mean (mu) is within your confidence interval?

A sample of 12 homes sold last week in St. Paul, Minnesota, is selected...

A sample of 12 homes sold last week in St. Paul, Minnesota, is selected. Can we conclude that as the size of the home (reported below in thousands of square feet) increases, the selling price (reported in $ thousands) also increases? Home Size Selling (thousands Price of square feet) ($ thousands)

Sample Size for 95% Confidence

Problem (also attached): 1) An Entomologist wishes to estimate the average development time of the citrus red mite correct to within .5 day. From previous experiments it is known that standard deviation is in the neighborhood of 4 days. How large a sample should the entomologist take to be 95% confident of her estimate.